Power line communication (PLC), also called Mains Communication, Power Line Transmission (PLT), Broadband Powerline (BPL), Powerband or Power Line Networking (PLN), is a term describing several different systems for using power distribution wires for simultaneous distribution of data. A carrier can communicate voice and data by superimposing an analog signal over the standard 50 or 60 Hz alternating current (AC). For indoor applications PLC equipment can use household electrical power wiring as a transmission medium. This is a technique used e.g. for in-home automation for remote control of lighting and appliances without installation of additional wiring.
In PLC systems the signals are transmitted and received in a differential mode (DM). Differential mode signaling is a method of transmitting information over pairs of wires. At DM signaling one wire carries the signal and the other wire carries the inverse of the signal, so that the sum of the voltages to ground on the two wires is always assumed to be zero. PLC modems therefore inject a DM signal between a neutral line and a phase line of an outlet of the power line network of the household for communication purposes. Another PLC modem can receive such DM signals at another outlet and use the DM signal for controlling an appliance associated with said receiving PLC modem.
However, at in-house power line grids, there are asymmetric elements between the phase line and the neutral line like a light switch, a current bar in the fuse cabinet, branches, etc. At these asymmetric elements, the DM signals injected by PLC modems are converted to Common Mode (CM) signals, thereby attenuating the DM signal which is added to attenuations due to other attenuation effects for the DM signal and thereby reducing coverage of PLC systems.
It is an object of the present invention to provide a method for transmitting and receiving a signal on a power line network that improves the coverage of PLC systems.
It is further object of the present invention to provide a transmitting unit for improving the coverage of PLC systems.
A still further object of the present invention is to provide a receiving unit for improving the coverage of PLC systems.
A further object of the present invention is to provide a system for improving the coverage of PLC systems.